A rivet is a type of fastener which generally includes a shank and a manufactured head formed at one end of the shank. When securing the rivet on a workpiece, a shop head is formed on the shank opposite the manufactured head for securing the workpiece between the heads formed on the rivet.
An impact gun or rivet gun is a known tool used for forming the shop head of a rivet. The rivet gun uses air pressure to drive a piston and a tool head connected thereto for impacting the rivet with a rivet snap secured in the tool head. In the riveting operation, a hardened steel bar or bucking bar is placed against the rivet shank to counter the pressure applied by the rivet gun on the manufactured head, thus forming the shop head.
The accessibility of the rivets to be installed however is not always ideal and thus rivet snaps are available in various sizes, shapes and lengths. Known variations of rivet snaps include offset, double offset and gooseneck types which are particularly useful when the rivet must be impacted at an angle of attack which is other than directly above and inline with the rivet. Each of these rivet snaps typically includes one or more bends in a shank of the rivet snap such that fixing the orientation of the rivet snap within the rivet gun is critical for engaging the rivet at the required angle of attack for urging the rivet against the bucking bar.
A problem with offset type rivet snaps arises when the rivet snaps rotate within the tool head of the rivet gun so as to interfere with the angle of attack of the rivet snap on the rivet. The misaligned rivet snap impacts the rivet improperly so as to damage and mar either the rivet, the workpiece or both. The damage to the rivet or workpiece can weaken the fastening strength of the rivet and the strength of the workpiece itself. Furthermore, marring removes the protective coating on the rivet and/or the workpiece, thus increasing the chance of early corrosion.
Rivet snaps are commonly secured within the tool head of the rivet gun using a spring retainer. The spring retainer however is only intended to retain the rivet snap within the tool head and does not resist the rotation of the rivet snap within the tool head which is known to occur.
To resist rotation of the rivet snap, an operator of the rivet gun is frequently required to hold the snap while riveting, however the operator is thus left without a free hand to manipulate the rivet gun or the workpiece while riveting as is often required. Rivet gun operators are thus known to place masking tape or other suitable material about a chamfered portion of the rivet snap which is arranged to be received within the tool head of the rivet gun. The use of tape increases the dimension of the rivet snap for increasing the friction of the rivet snap engaged within the tool head. Masking tape however requires frequent replacement which is time consuming and messy due to the adhesive of the tape.